U.S. patent number 7,162,356 [Application Number 10/854,712] was granted by the patent office on 2007-01-09 for control apparatus and control method for internal combustion engine.
This patent grant is currently assigned to Denso Corporation, Toyota Jidosha Kabushiki Kaisha. Invention is credited to Hisayo Dohta, Naohide Fuwa.
United States Patent |
7,162,356 |
Fuwa , et al. |
January 9, 2007 |
Control apparatus and control method for internal combustion
engine
Abstract
A control apparatus for an internal combustion engine provided
with a fuel supply mechanism capable of adjusting a fuel supply
amount includes a flow rate sensor that detects an intake air flow
rate that represents a flow rate of air admitted into a combustion
chamber of the internal combustion engine, a pressure sensor that
detects a pressure of the air admitted into the combustion chamber
of the internal combustion engine, a characteristic change
estimation unit that estimates a characteristic change of the
internal combustion engine in accordance with the intake air flow
rate detected by the flow rate sensor and the intake air pressure
detected by the pressure sensor, and a fuel supply mechanism
control unit that controls the fuel supply mechanism. The fuel
supply mechanism control unit controls the fuel supply mechanism
such that the characteristic change in the internal combustion
engine is compensated in accordance with an estimation performed by
the characteristic change estimation unit.
Inventors: |
Fuwa; Naohide (Toyota,
JP), Dohta; Hisayo (Chiryu, JP) |
Assignee: |
Toyota Jidosha Kabushiki Kaisha
(Toyota, JP)
Denso Corporation (Kariya, JP)
|
Family
ID: |
33534533 |
Appl.
No.: |
10/854,712 |
Filed: |
May 27, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050010354 A1 |
Jan 13, 2005 |
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Foreign Application Priority Data
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May 27, 2003 [JP] |
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2003-149305 |
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Current U.S.
Class: |
701/104;
123/568.11; 123/90.15; 701/105; 123/478 |
Current CPC
Class: |
F02D
41/182 (20130101); F01L 13/0015 (20130101); F02D
41/2464 (20130101); F02D 41/2422 (20130101); F01L
2800/00 (20130101); F02D 41/0055 (20130101); F01L
3/00 (20130101); F02D 2041/001 (20130101); F01L
9/20 (20210101); F01L 2009/2126 (20210101); F02D
41/0002 (20130101) |
Current International
Class: |
B60T
7/12 (20060101); F02M 51/00 (20060101) |
Field of
Search: |
;701/101,104,105
;123/478,480,90.15,568.11 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kwon; John T.
Attorney, Agent or Firm: Oliff & Berridge, PLC
Claims
What is claimed is:
1. A control apparatus that controls an internal combustion engine
including a valve adjustment mechanism that is capable of adjusting
at least one of a lift amount and an operation angle of a valve,
the control apparatus comprising: a characteristic change
estimation unit that estimates a characteristic change in the
internal combustion engine in accordance with a predetermined
condition; and a valve adjustment mechanism control unit that
controls the valve adjustment mechanism, wherein the valve
adjustment mechanism control unit controls the valve adjustment
mechanism such that the characteristic change in the internal
combustion engine is compensated in accordance with the estimation
performed by the characteristic change estimation unit.
2. The control apparatus according to claim 1, wherein the
characteristic change estimation unit estimates a mechanical
characteristic change in the valve adjustment mechanism including a
change in an amount of at least one of the lift amount and the
operation angle of the valve.
3. The control apparatus according to claim 1, wherein the
characteristic change estimation unit estimates a change in an
intake air characteristic of the internal combustion engine.
4. The control apparatus according to claim 3, wherein the change
in the intake air characteristic comprises an aerodynamic
characteristic change including a change in a pressure loss on a
path where air is admitted into the combustion chamber of the
internal combustion engine.
5. The control apparatus according to claim 1, wherein the
characteristic change estimation unit performs an estimation when
the internal combustion engine is in a predetermined normal
operation state where a load and an engine speed of the internal
combustion engine are held within a predetermined range for a
predetermined time period.
6. The control apparatus according to claim 1, wherein the internal
combustion engine is capable of executing a purging control under
which the fuel vaporized within a fuel tank is released into the
intake air, and wherein the characteristic change estimation unit
performs the estimation when the purging control is not
executed.
7. The control apparatus according to claim 1, wherein the internal
combustion engine is capable of executing an EGR control under
which an exhaust gas is partially mixed with the intake air so as
to be re-circulated, and wherein the characteristic change
estimation unit performs the estimation when the EGR control is not
executed.
8. The control apparatus according to claim 1, wherein the valve
adjustment mechanism control unit is capable of executing a
calibration operation so as to confirm a reference position of the
valve adjustment mechanism, and wherein the characteristic change
estimation unit performs the estimation after completion of the
calibration operation.
9. The control apparatus according to claim 1, wherein the
characteristic change estimation unit performs the estimation in
accordance with a combination of the engine speed of the internal
combustion engine and an adjustment position of the valve
adjustment mechanism.
10. The control apparatus according to claim 1, wherein the
characteristic change estimation unit performs the estimation at
every valve opening time area obtained by integrating the lift
amount of the valve with time.
11. An internal combustion engine comprising: a valve adjustment
mechanism capable of adjusting at least one of a lift amount and an
operation angle of a valve; a characteristic change estimation unit
that estimates a characteristic change in the internal combustion
engine in accordance with a predetermined condition the intake air
flow rate detected by the flow rate sensor and the intake air
pressure detected by the pressure sensor; and a valve adjustment
mechanism control unit that controls the valve adjustment
mechanism, wherein the valve adjustment mechanism control unit
controlling the valve adjustment mechanism such that the
characteristic change in the internal combustion engine is
compensated in accordance with the estimation performed by the
characteristic change estimation unit.
12. A control apparatus according to claim 1, further comprising
one of a flow rate sensor that detects an intake air flow rate that
represents a flow rate of air admitted into a combustion chamber of
the internal combustion engine and a pressure sensor that detects
an intake air pressure that represents a pressure of the air
admitted into the combustion chamber of the internal combustion
engine, wherein the characteristic change estimation unit that
estimates the characteristic change in the internal combustion
engine in accordance with one of the intake air flow rate detected
by the flow rate sensor and the intake air pressure detected by the
pressure sensor.
13. The control apparatus according to claim 1, further comprising:
a flow rate sensor that detects an intake air flow rate that
represents a flow rate of air admitted into a combustion chamber of
the internal combustion engine; and a pressure sensor that detects
an intake air pressure that represents a pressure of the air
admitted into the combustion chamber of the internal combustion
engine, wherein the characteristic change estimation unit that
estimates the characteristic change in the internal combustion
engine in accordance with the intake air flow rate detected by the
flow rate sensor and the intake air pressure detected by the
pressure sensor.
14. A control method that controls an internal combustion engine
including a valve adjustment mechanism that is capable of adjusting
at least one of a lift amount and an operation angle of a valve,
the control method comprising the steps of: estimating a
characteristic change in the internal combustion engine in
accordance with a predetermined condition the intake air flow rate
and the intake air pressure; and controlling the valve adjustment
mechanism such that the charateristic change in the internal
combustion engine is compensated in according with the estimation.
Description
INCORPORATED BY REFERENCE
The disclosure of Japanese Patent Applications No. 2003-149305
filed on May 27, 2003 including the specification, drawings and
abstract is incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a control technology for an internal
combustion engine mounted in a vehicle.
2. Description of Related Art
An air fuel ratio control (fuel injection control) technology with
higher accuracy becomes indispensable for coping with emission
regulations that has been becoming increasingly severe year by
year. In order to realize the air fuel ratio control with higher
accuracy, the accuracy of calculating an amount of air charged in
the cylinder, that is, intake air amount within a combustion
chamber of an internal combustion engine has to be further
improved. Such calculation has been disclosed in the United States
Patent Application Publication No. 2002/0107630 A1 in which the
amount of air within the cylinder is calculated using an intake
system model, for example. The intake system model is intended to
clarify the behavior of the intake air that flows from the throttle
valve to the intake port of the combustion chamber.
The behavior of the intake air that flows through the intake
passage will vary with aging, for example, sediments deposited on
the intake passage. Accordingly, the actual behavior of the intake
air may not accord with the behavior in the intake system model,
resulting in an error in the estimated amount of air within the
cylinder. An opening/closing characteristic of a valve provided in
the intake port of the combustion chamber will also vary with
aging, for example, mechanical wear or deformation of a valve
system and the like. This may also cause the error in the estimated
amount of air in the cylinder. Such error is caused not only by the
aging as aforementioned but also by the piece-to-piece variation
among internal combustion engines at a stage immediately after
producing thereof.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a technology for
preventing deterioration in performance of the air fuel ratio
control owing to aging or piece-to-piece variation among internal
combustion engines.
According to a first aspect of the invention, a control apparatus
that controls an internal combustion engine includes a fuel supply
mechanism capable of adjusting a fuel supply amount. The control
apparatus is further provided with a characteristic change
estimation unit that estimates a characteristic change in the
internal combustion engine in accordance with a predetermined
condition, wherein the fuel supply mechanism control unit controls
the fuel supply mechanism such that the characteristic change in
the internal combustion engine is compensated in accordance with an
estimation performed by the characteristic change estimation
unit.
According to a first aspect of the invention, the characteristic
change in the internal combustion engine is estimated based on the
predetermined condition. The characteristic change is compensated
by correcting quantity of the fuel to be supplied in accordance
with the estimated value. This makes it possible to prevent
deterioration in performance of the air fuel ratio control owing to
aging or piece-to-piece variation among internal combustion
engines.
In the first aspect of the invention, the control apparatus may
further comprise one or both of a flow rate sensor that detects an
intake air flow rate that represents a flow rate of air admitted
into a combustion chamber of the internal combustion engine and a
pressure sensor that detects an intake air pressure that represents
a pressure of the air admitted into the combustion chamber of the
internal combustion engine. The characteristic change estimation
unit may estimate the characteristic change in the internal
combustion engine in accordance with one or both of the intake air
flow rate detected by the flow rate sensor and the intake air
pressure detected by the pressure sensor.
In the first aspect of the invention, the internal combustion
engine includes a valve adjustment mechanism that is capable of
adjusting at least one of a lift amount and an operation angle of a
valve, and the control apparatus may further include a valve
adjustment mechanism control unit that controls the valve
adjustment mechanism.
The aforementioned structure gives an advantageous effect
especially to the internal combustion engine provided with a valve
lift adjustment mechanism because the characteristics of this type
of the internal combustion engine tend to considerably vary with
aging. More specifically, the aforementioned internal combustion
engine is supposed to be operated with a relatively smaller valve
lift amount. In the course of such operation, the intake air amount
within the cylinder may be greatly affected by sediments deposited
around the valve or the intake port leading to the combustion
chamber.
According to a second aspect of the invention, a control apparatus
that controls an internal combustion engine includes a valve
adjustment mechanism that is capable of adjusting at least one of a
lift amount and an operation angle of a valve. The control
apparatus is provided with a characteristic change estimation unit
that estimates a characteristic change in the internal combustion
engine in accordance with a predetermined condition, and a valve
adjustment mechanism control unit that controls the valve
adjustment mechanism. The valve adjustment mechanism control unit
controls the valve adjustment mechanism such that the
characteristic change in the internal combustion engine is
compensated in accordance with an estimation performed by the
characteristic change estimation unit.
In the second aspect of the invention, the characteristic change of
the internal combustion engine is estimated based on the intake air
flow rate and the intake air pressure. It may be compensated by
correcting the valve lift amount in accordance with the estimated
value. This makes it possible to prevent deterioration in
performance of the air fuel ratio control owing to aging or
piece-to-piece variation among internal combustion engines.
In the second aspect of the invention, the control apparatus may
further comprise one or both of a flow rate sensor that detects an
intake air flow rate that represents a flow rate of air admitted
into a combustion chamber of the internal combustion engine and a
pressure sensor that detects an intake air pressure that represents
a pressure of the air admitted into the combustion chamber of the
internal combustion engine. The characteristic change estimation
unit may estimate the characteristic change in the internal
combustion engine in accordance with one or both of the intake air
flow rate detected by the flow rate sensor and the intake air
pressure detected by the pressure sensor.
In the aforementioned control system, the characteristic change
estimation unit may estimate a mechanical characteristic change in
the valve adjustment mechanism including a change in an amount of
at least one of the lift amount and the operation angle of the
valve. In the aforementioned control apparatus, the characteristic
change estimation unit may estimate a change in an intake air
characteristic of the internal combustion engine. The change in the
intake air characteristic may be an aerodynamic characteristic
change which includes a change in a pressure loss on a path where
air is admitted into the combustion chamber of the internal
combustion engine.
In the aforementioned control apparatus, the characteristic change
estimation unit may be structured to perform an estimation when the
internal combustion engine is in a predetermined normal operation
state where a load and an engine speed of the internal combustion
engine are held within a predetermined range for a predetermined
time period.
In the aforementioned control apparatus, the behavior of the intake
air may be estimated in a stable state, improving accuracy in
estimating the characteristic change of the internal combustion
engine.
In the aforementioned control system, the internal combustion
engine is capable of executing a purging control under which the
fuel vaporized within a fuel tank is released into the intake air
or an EGR control under which exhaust gas is partially mixed with
the intake air so as to be re-circulated. The characteristic change
estimation unit may be structured to perform the estimation when
the purging control or the EGR control is not executed.
Under the purging control or EGR control, the behavior of the
intake air may fluctuate to deteriorate the estimation accuracy. If
the estimation is performed in the time at which the purging
control or the EGR control is not executed, deterioration in the
estimation accuracy caused by the purging control or the EGR
control may be avoided.
In the aforementioned control system, the valve adjustment
mechanism control unit is capable of executing a calibration
operation so as to confirm a reference position of the valve
adjustment mechanism. The characteristic change estimation unit may
be structured to perform the estimation after completion of the
calibration operation.
The accuracy in the control of the valve adjustment mechanism
cannot be ensured unless calibration is completed. Deterioration in
accuracy of the control of the valve adjustment mechanism may be
avoided by performing the estimation after completion of
calibration.
In the aforementioned control system, the characteristic change
estimation unit may be structured to perform the estimation in
accordance with a combination of the engine speed of the internal
combustion engine and an adjustment position of the valve
adjustment mechanism. In the aforementioned control system, the
characteristic change estimation unit may also be structured to
perform the estimation at every valve opening time area obtained by
integrating the lift amount of the valve with time. In the case
where the internal combustion engine is not provided with the valve
adjustment mechanism, the adjustment position thereof is used as a
fixed value.
According to a third aspect of the invention, an internal
combustion engine includes a fuel supply mechanism capable of
adjusting a fuel supply amount. The internal combustion engine
includes a control apparatus provided with a characteristic change
estimation unit that estimates a characteristic change in the
internal combustion engine in accordance with a predetermined
condition, and a fuel supply mechanism control unit that controls
the fuel supply mechanism, the fuel supply mechanism control unit
controlling the fuel supply mechanism such that the characteristic
change in the internal combustion engine is compensated in
accordance with an estimation performed by the characteristic
change estimation unit.
According to a fourth aspect of the invention, an internal
combustion engine includes a valve adjustment mechanism capable of
adjusting at least one of a lift amount and an operation angle of a
valve. The internal combustion engine includes a control apparatus
provided with, a characteristic change estimation unit that
estimates a characteristic change in the internal combustion engine
in accordance with a predetermined condition, and a valve
adjustment mechanism control unit that controls the valve
adjustment mechanism, the valve adjustment mechanism control unit
controlling the valve adjustment mechanism such that the
characteristic change in the internal combustion engine is
compensated in accordance with an estimation performed by the
characteristic change estimation unit.
According to a fifth aspect of the invention, a measurement
apparatus that measures an amount of air charged in a cylinder as
an amount of air admitted into a combustion chamber of an internal
combustion engine. The measurement apparatus is provided with a
characteristic change estimation unit that estimates a
characteristic change in the internal combustion engine in
accordance with a predetermined condition, and an in-cylinder air
charging amount calculation unit capable of correcting an amount of
air charged in the cylinder so as to compensate the characteristic
change in the internal combustion engine in accordance with an
estimation performed by the characteristic change estimation
unit.
It is to be understood that the invention may be realized in the
form of a method of controlling the internal combustion engine, an
internal combustion engine provided with the aforementioned control
apparatus, a measurement device and a method that measure the
amount of air within the cylinder of the internal combustion
engine, or any other form so long as it does not depart from spirit
and scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and further objects, features and advantages of the
invention will become apparent from the following description of
preferred embodiments with reference to the accompanying drawings,
wherein like numerals are used to represent like elements and
wherein:
FIG. 1 is a schematic view that shows a structure of an internal
combustion engine and a control unit thereof as an embodiment of
the invention;
FIG. 2 is an explanatory view that relates to an adjusting
operation of an opening/closing timing of an intake valve by a
variable valve train system;
FIG. 3 is a block diagram of the variable valve train system in a
first embodiment;
FIG. 4A and FIG. 4B are explanatory views each showing how an
operation angle is aerodynamically estimated;
FIG. 5 is a flowchart representing a control routine of correction
in the first embodiment;
FIG. 6 is a flowchart representing a control routine of determining
a correction value in the first embodiment;
FIG. 7 is a flowchart representing a control routine of executing
the correction in the first embodiment;
FIG. 8 is a block diagram of the variable valve train system in a
second embodiment;
FIG. 9 is an explanatory view that shows each value of correction
amounts Ea' calculated in the second embodiment;
FIGS. 10A and 10B are explanatory views showing each value of
correction amount Ea'' calculated in a third embodiment;
FIGS. 11A and 11B are conceptual views each representing an area in
the valve-opening time in the third embodiment; and
FIG. 12 is a block diagram of a fuel supply control system
according to a fourth embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Preferred embodiments of the invention will be described in the
following sections: A. Structure; B. Valve train control system
according to a first embodiment; C. Valve train control system
according to a second embodiment; D. Valve train control system
according to a third embodiment; E. Valve train control system
according to a fourth embodiment; and F. Modified embodiment.
A. Structure
FIG. 1 is an explanatory view that shows a structure of an internal
combustion engine and a control system thereof as a preferred
embodiment of the invention. The control system is structured to
control a gasoline engine 100 as an internal combustion engine
mounted in a vehicle. The engine 100 is provided with an intake
pipe 110 for supplying air (new air) into a combustion chamber, and
an exhaust pipe 120 for discharging exhaust gas from the combustion
chamber to the outside. The combustion chamber is provided with a
fuel injection valve 101 for injecting the fuel into the combustion
chamber, a spark plug 102 for igniting air/fuel mixture within the
combustion chamber, an intake valve 322, and an exhaust valve
362.
The intake pipe 110 is provided with an air flow meter 130 (flow
rate sensor) that detects an intake air flow rate, a throttle valve
132 that adjusts the intake air flow rate, and a surge tank 134
arranged in the order from upstream of the intake pipe 110. The
surge tank 134 is provided with an intake air temperature sensor
136 and an intake air pressure sensor 138. An intake air passage of
the surge tank 134 at the downstream side is split into a plurality
of branch pipes each connected to the corresponding combustion
chambers. In FIG. 1, however, only a single branch pipe is shown
for simplifying the description. The exhaust pipe 120 is provided
with an air/fuel ratio sensor 126 and a catalyst 128 that
eliminates harmful component contained within the exhaust gas. The
air flow meter 130 or the pressure sensor 138 may be placed on the
position other than those described above. In this embodiment, the
fuel is directly injected into the combustion chamber. However, the
fuel may be injected into the intake pipe 110.
Intake/discharge operation of the engine 100 is selected in
accordance with each opening/closing state of the intake valve 322
and the exhaust valve 362. The intake valve 322 and the exhaust
valve 362 are connected to variable valve train systems 320, 360,
respectively such that the respective valve-opening characteristics
can be changed. Those variable valve train systems 320, 360 are
capable of changing the operation angle and the opening/closing
timing with respect to the crankshaft. The aforementioned variable
valve train system may be employed as disclosed in the U.S. Pat.
No. 6,425,357. Alternatively, it is possible to employ the variable
valve train system that is capable of changing the operation angle
and the phase using an electromagnetic valve.
The variable valve train systems 320, 360 are connected to valve
train adjustment actuators 220, 260, respectively. Those valve
train adjustment actuators 220, 260 are feedback controlled by a
control unit 10 to be described in detail below.
The operation of the engine 100 is controlled by the control unit
10. The control unit 10 is formed as a micro-computer including
CPU, RAM, and ROM therein. The control unit 10 receives signals
from various sensors. Those sensors include not only the
aforementioned sensors 136, 138, 126 but also a knock sensor 104, a
water temperature sensor 106 that detects a water temperature in
the engine, an engine speed sensor 108 that detects the engine
speed, and an accelerator sensor 109.
The control unit 10 includes a timing command section 12 for
setting an operation timing of the valves 322, 362 with respect to
the crankshaft, and an operation angle command section 14 for
setting the operation angle of the valves 322, 362. Those sections
are capable of controlling the variable valve train systems 320,
360 based on the engine speed, load, and water temperature of the
engine 100. The control unit 10 further includes a fuel supply
control section 16 for controlling quantity of the fuel supplied to
the combustion chamber by the fuel injection valve 101, and a
variable valve train estimation section 15 for estimating the state
change in each of the variable valve train systems 320, 360 owing
to aging. The respective functions of those sections will be
described later.
FIG. 2 is an explanatory view that shows how the open/close timing
of the intake valve 322 is adjusted by the variable valve train
system 320. The variable valve train system 320 in this embodiment
is structured to change the operation angle .theta. and the lift
amount at the same time. The open/close timing .phi., that is, the
center of the valve-opening period with respect to the crankshaft
is adjusted by the variable valve timing mechanism of the variable
valve train system 320.
The variable valve train system 320 is capable of changing the
operation angle of the intake valve 322 independent of changing of
the operation timing thereof with respect to the crankshaft.
Therefore, the operation angle of the intake valve 322 and the
operation timing thereof with respect to the crankshaft can be set
to appropriate values independently. The variable valve train
system 360 for the exhaust valve 362 exhibits the same
characteristics as those of the variable valve train system
320.
B. Valve Train Control System of the First Embodiment:
FIG. 3 is a block diagram of the valve train control system of the
first embodiment. The valve train control system is structured to
compensate the substantial reduction in the operation angle Ev (see
FIG. 3) of the valve owing to aging of the variable valve system
320. This embodiment becomes effective especially when it is known
that the main cause of change in the subject to be controlled as an
elapse of time is the substantial reduction in the operation angle
of the valve owing to aging of the variable valve system 320. The
operation angle .theta.v is set as the nominal operation angle on
the assumption that there is no change owing to aging.
Wear of the cam (not shown) of the valve or deformation of the
locker arm (not shown) may cause substantial reduction in the
operation angle of the valve resulting from aging of the variable
valve system 320. Accordingly, the valve train state estimation
section 15 is operable on the assumption that the substantial
reduction in the operation angle of the valve is held constant
irrespective of the operation state.
The valve train control system of the embodiment is realized by the
valve train adjustment mechanism actuator 220 feedback controlled
by the ECU 10. The feedback control to the valve train adjustment
mechanism actuator 220 is realized by measuring a mechanical
operation amount .delta.a of the valve train adjustment mechanism
actuator 220 which is feedbacked to the ECU 10. Then the valve
train adjustment mechanism actuator 220 is controlled such that the
mechanical operation amount .delta.a becomes close to a target
value (.delta.c+Ea) output from the operation angle command section
14. The measurement error of the actuator sensor 250 is assumed to
be negligible for the purpose of simplifying the description.
The target value (.delta.c+Ea) is obtained by adding the nominal
lift amount .delta.c corresponding to the nominal operation angle
.theta.v to the correction value Ea (compensated lift amount) for
compensating the substantial reduction amount Ev owing to aging of
the variable valve system 320. The nominal lift amount .delta.c is
set in accordance with the engine speed Ne of the engine 100 in
reference to the operation angle map (not shown) stored in the
operation angle command section 14.
The correction amount Ea is derived from the intake pressure Ps
input from the intake/exhaust mechanism 150, intake air flow rate
Ms, intake air temperature Ts, mechanical operation amount .delta.a
input from the actuator sensor 250, and the engine speed Ne. The
intake air pressure Ps as the pressure within the surge tank 132
(FIG. 1) is measured by the intake air pressure sensor 138. The
intake air flow rate Ms as the flow rate of air (new air) within
the intake pipe 110 is measured by the air flow meter 130. The
intake air temperature Ts as the temperature of air within the
surge tank 13 is measured by the intake air temperature sensor
136.
The correction amount Ea can be calculated using measured value and
the valve train system state estimation map 15M. The map 15M
includes a plurality of maps each prepared as a combination of the
engine speed Ne and the intake air temperature Ts. Each of the maps
represents the relationship among the intake air pressure Ps, the
intake air flow rate Ms, and the operation angle .theta.,
respectively.
The valve train state estimation section 15 calculates the
correction amount Ea in the following manner: (1) An appropriate
map is selected among the group of maps in accordance with the
engine speed Ne and the intake air temperature Ts; (2) An
aerodynamic estimated operation angle .theta.ea is calculated based
on the intake air pressure Ps and the intake air flow rate Ms in
reference to the map (described later); and (3) A mechanical
estimated operation angle .theta.e.delta. is derived from a
mechanical operation amount .delta.a input from the actuator sensor
250. The calculation is performed based on the predetermined
relationship between the mechanical operation amount .delta.a of
the actuator 220 and the operation angle of the valve. In this
case, the reduction in the operation angle of the valve owing to
aging is not considered for the aforementioned relationship.
FIGS. 4A and 4B show how the operation angle is aerodynamically
estimated. FIG. 4A shows the intake/exhaust mechanism 150 as an
essential portion of the gasoline engine 100 shown in FIG. 1. FIG.
4B represents the linear model of the intake/exhaust mechanism 150
in the form of an electric circuit. The stable state of both the
load and the engine speed Ne of the gasoline engine is linearly
approximated to this linear model. In the linear model, the flow of
air is replaced by the electric current. Accordingly the potential
difference of resistance corresponds to the pressure loss.
Each element of the intake/exhaust mechanism 150 corresponds to the
element of the linear model shown in FIG. 4B as follows. The
outside air corresponds to the ground G, the air flow meter 130
corresponds to an ampere meter 130e, the intake pipe 110 that
admits intake air corresponds to a conductor 110e, and the throttle
valve 132 that adjusts the intake air amount corresponds to a
variable resistance 132e. The surge tank 134 that suppresses the
fluctuation in the intake air pressure corresponds to a capacitor
134e, the intake air pressure sensor 138 that measures the intake
air pressure corresponds to a voltmeter 138e, the intake valve 322
that adjusts the intake air supplied to the combustion chamber
corresponds to the variable resistance 322e, the exhaust valve 362
that adjusts the exhaust gas discharged from the combustion chamber
corresponds to the variable resistance 362e, and the cylinder 170
and the piston 171 each functioning aerodynamically as the pump
correspond to a battery 170e.
When the load and the engine speed Ne of the gasoline engine 100
are in the stable state, the voltage of the battery 170e as the
corresponding element is also in the stable state. Assuming that
the current flowing through the series circuit formed of the
variable resistance 322e, battery 170e, the variable resistance
362e, and the potential difference in the series circuit are
measured, the resistance value of the series circuit may be
calculated. The current can be measured by the ampere meter 130e,
and the voltage can be measured by the voltmeter 138e.
If the voltage of the battery 170e is further determined, the
aforementioned two values of the variable resistances 322e, 362e
can be calculated. Meanwhile the amount corresponding to the
voltage of the battery 170e can also be determined in accordance
with the engine speed Ne. It is clarified that the calculation can
be performed even if the resistance value of the variable
resistance 132e corresponding to the throttle valve 132 cannot be
determined.
When the load and the engine speed Ne of the gasoline engine 100
are in the stable state, each operation angle .theta. of the valves
322, 362 corresponding to the variable resistance values 322e, 362e
can be estimated based on the intake air pressure Ps and the intake
air flow rate Ms.
The valve train state estimation section 15 calculates the
difference between the estimated operation angles .theta.ea and
.theta.e.delta. as the error in the operation angle .theta. owing
to aging. The error in the operation angle .theta. is further
converted into the operation amount of the actuator sensor 250 so
as to calculate the correction amount Ea.
FIG. 5 is a flowchart showing a control routine of correction
executed in the first embodiment according to the invention. In the
control routine for the correction, the characteristic change in
the subject to be controlled owing to aging is compensated by
correcting the operation angle of the valve. In step S1000, the
valve train state estimation section 15 (see FIG. 3) of the ECU 10
determines the correction amount Ea as the correction value. In
step S2000, the operation angle command section 14 updates the
correction value at a timing so as not to exert an excessive
influence to the drivability. The aforementioned process is
continuously executed until the ignition is set to OFF state in
step S3000.
FIG. 6 is a flowchart showing a control routine of the process for
determining a correction value in the first embodiment according to
the invention. In step S1100, it is determined whether it is
possible to perform the state estimation, that is, it is possible
to aerodynamically estimate the operation angle.
In this embodiment, it is determined that the estimation can be
performed when the following conditions are established. (1) Each
measurement value of the intake air pressure sensor 138 and the air
flow meter 130 is in a reliable state, for example, where those
measurement values of the intake air pressure sensor 138 and the
air flow meter 130 are in the convergent state and measure the
value other than an excessively large or small one. (2) Purging
control or EGR control is not executed in the intake/exhaust
mechanism 150. The purging control is executed by releasing the
fuel vaporized within the fuel tank (not shown) into the surge tank
134 so as not to increase the pressure within the fuel tank to an
excessively large value. The EGR control is executed by mixing the
exhaust gas partially with the intake air so as to be recirculated.
The purging control or the EGR control executed during the
estimation may change the aerodynamic behavior within the
intake/exhaust mechanism 150. As a result, the reliability of the
measurement values of the intake air flow rate measured by the air
flow meter 130 may be deteriorated. That is why the estimation is
performed when the purging control or the EGR control is not
executed. (3) Learning (calibration) of the reference positions of
both the intake valve 322 and the exhaust valve 362 are completed.
The learning is realized by mechanically making the actuator 220
for the valve train adjustment mechanism bottomed.
If it is determined that it is not possible to perform the state
estimation in step S1200, the process proceeds to step S1600 where
the counter is cleared. The process then returns to step S1100
where it is determined whether it is possible to perform the state
estimation. Meanwhile if it is determined that it is possible to
perform the state estimation in step S1200, the process proceeds to
step S1300.
In step S1300, the ECU 10 stores the measurement value of the
intake air pressure Ps obtained from the intake air pressure sensor
138 in the RAM (not shown). Then in step S1400, the ECU 10 stores
the measurement value of the intake air flow rate Ms obtained from
the air flow meter 130 to another address in the RAM.
In step S1500, it is determined whether the gasoline engine 100 is
operated in a normal state, that is, the engine speed Ne and the
load (torque) are held substantially constant. More specifically,
when each of the measurement values such as the engine speed Ne is
within a range between +5% and -5% of the respective average value,
it may be determined that the engine 100 is operated in the normal
state. In order to improve the estimation accuracy, it may be
determined whether not only the engine speed Ne and the load of the
engine but also the intake air pressure Ps and the intake air flow
rate Ms are held substantially constant.
If it is determined that the engine 100 is not in the normal state
in step S1500, the process proceeds to step S1600 where the counter
is cleared. The process then returns to step S100. Meanwhile if it
is determined that the engine 100 is operated in the normal state
in step S1500, the process proceeds to step S1700 where the counter
value is incremented. The process then proceeds to step S1800.
In step S1800, it is determined whether the counter value is larger
than a predetermined value. The determination is made as to whether
the normal state is continued for the time interval required for
determining the correction value (3 seconds, for example). If the
counter value is equal to or smaller than the predetermined value,
the process returns to step S1100 without clearing the counter
value. If the counter value exceeds the predetermined value, the
process proceeds to step S1900.
In step S1900, the valve train state estimation section 15 (see
FIG. 3) calculates the correction amount Ea as the correction value
in the manner as described above. The newly calculated correction
value Ea is transmitted to the operation angle command section 14
so as to store the received correction amount Ea in the RAM.
FIG. 7 is a flowchart of the control routine for the process of
correction executed in the first embodiment. The process for
updating the correction value is executed to update the correction
amount Ea at a timing so as not to give an excessive influence on
the drivability. The aforementioned process is necessary to prevent
an emergent fluctuation in the torque owing to updating of the
correction value.
In step S2100, the operation angle command section 14 calculates
the updating difference as the difference between the calculated
correction amount Ea and the correction amount that has been
currently used. When the correction is not performed, the
correction amount that has been currently used is regarded as being
zero.
In step S2200, it is determined whether the updating difference is
larger than a predetermined value. If the updating difference is
equal to or smaller than the predetermined value, the operation
angle command section 14 determines that the correction is not
necessary. The process then returns to the process for determining
the correction value (see FIG. 6, and step S3000 in FIG. 5). If the
updating difference is larger than the predetermined value, the
process proceeds to step S2300.
In step S2300, it is determined whether the ignition is in OFF
state. If the ignition is in OFF state, updating of the correction
value is allowed without affecting the drivability. If it is
determined that the ignition is in OFF state in step S2300, the
process proceeds to step S2700 where the correction value is
updated. In this way, the correction amount Ea that is output
together with the nominal lift amount .delta.c from the operation
angle command section 14 is updated in the state where the ignition
is held OFF such that the drivability is not affected. If it is
determined that the ignition is in ON state in step S2300, the
process proceeds to step S2400.
In step S2400, it is determined whether the gasoline engine 100 is
in an idling state. If the engine 100 is in the idling state, the
correction value can be updated without affecting the drivability
even if the ignition is in ON state. The determination with respect
to the idling state of the engine may be performed in accordance
with the input signal from, for example, the accelerator sensor
109. If it is determined that the engine 100 is in the idling state
in S2400, the process proceeds to step S2700 where the correction
value is updated. If it is determined that the engine 100 is not in
the idling state in S2400, the process proceeds to step S2500. The
fuel cut state where the fuel is not supplied to the internal
combustion engine may be regarded as the state similar to the
idling state.
In step S2500, it is determined whether the gasoline engine 100 is
in a predetermined operation state, that is, whether each of the
operation angles of the valves 322, 362 is larger than a
predetermined angle. When the engine is in the operation state
where the operation angle is relatively large, the degree of change
in the operation angle may be relatively smaller depending on the
correction value even if the correction value is updated. This
makes it possible to update the correction value without
excessively affecting the drivability.
The determination as to whether the gasoline engine 100 is in the
predetermined operation state may be made in accordance with the
nominal lift amount .delta.c (containing no correction amount)
output from the operation angle command section 14. If the engine
100 is in the predetermined operation state, the process proceeds
to step S2600 where it is determined whether the correction value
is smaller than a predetermined value. If the correction value is
smaller than the predetermined value, the process proceeds to step
S2700 where the correction value is updated. If the engine 100 is
not in the predetermined operation state, or the correction value
is equal to or larger than the predetermined value, the process
then returns to the process for determining the correction value
(FIG. 6, and step S3000 in FIG. 5). The predetermined value is
preliminarily set as the value that allows updating of the
correction value without excessively affecting the drivability in
the predetermined operation state.
The control system according to the first embodiment compensates
the mechanical characteristic change such as reduction in the valve
lift amount owing to aging of the variable valve train mechanism
320 by correcting the operation angle of the valve. As a result,
the error in the amount of air admitted into the combustion chamber
is reduced. This makes it possible to suppress deterioration in the
air fuel ratio control owing to aging or piece-to-piece variation
among the internal combustion engines.
The operation angle of the valve is corrected at a timing so as not
to excessively affect the drivability. This makes it possible to
suppress the influence exerted to the drivability resulting from
correcting the operation angle.
C. Valve Train Mechanism Control System in Second Embodiment
FIG. 8 is a block diagram of the valve train mechanism control
system according to a second embodiment of the invention. The valve
train control system of this embodiment is different from that of
the first embodiment in that the structure for compensating not
only the reduction in the valve lift amount Ev of the valve owing
to aging of the variable valve train mechanism 320 (see FIGS. 3, 8)
but also the increase in the air resistance (increase in the
pressure loss) owing to aging of the intake/exhaust system 150.
The increase in the air resistance owing to aging of the
intake/exhaust mechanism 150 is expressed as the reduced valve lift
amount Ep (see FIG. 8). This is because the increase in the air
resistance of the intake/exhaust pipe can be considered as being
qualitatively equivalent to the reduced valve lift amount.
This embodiment is effective especially when it is preliminarily
obvious that not only reduction in the valve lift amount of the
variable valve mechanism 320 but also increase in the air
resistance due to sediment on the intake valve 110 or the exhaust
valve 120 of the intake/exhaust mechanism 150 are regarded as an
important factor of the change in the subject to be controlled
owing to aging.
The valve train control system of the second embodiment is
different from that of the first embodiment in the use of the ECU
10a in place of the ECU 10. The ECU 10a is provided with an
intake/exhaust system state estimation section 15a in place of the
intake/exhaust system state estimation section 15. The
intake/exhaust system state estimation section 15 is structured on
the assumption that the substantial reduction in the valve lift
amount is constant irrespective of the engine operation state.
Meanwhile, the intake/exhaust system state estimation section 15a
of the second embodiment is structured on the assumption that the
substantial reduction in the valve lift amount (Ev+Ep) is likely to
change depending on the engine operation state.
The increase in the air resistance owing to aging of the
intake/exhaust mechanism 150 is considered as being qualitatively
equivalent to the reduced amount Ep of the valve lift amount.
Accordingly, the same map as the valve train state estimation map
15M for the first embodiment may be used in the second embodiment
for calculating the correction amount in the same manner as in the
first embodiment.
FIG. 9 is an explanatory view that shows the correction amount Ea'
calculated in the second embodiment of the invention. Unlike the
first embodiment where a single correction amount Ea is calculated,
the correction amount Ea' is calculated under the respective
conditions (combination of the engine speed Ne and the operation
angle .theta.) in the second embodiment. In this embodiment, the
engine speed Ne corresponds to the engine speed of the internal
combustion engine, and the operation angle .theta. corresponds to
the adjustment position of the valve adjustment mechanism.
Referring to FIG. 9, in the range of the engine speed Ne between
801 and 1600 rpms, the correction amount Ea' is calculated as one
combination at the operation angle between 111 and 120 degs. In the
range of the engine speed Ne between 1601 and 2400 rpms, the
correction amount Ea' is calculated as two combinations at the
operation angle between 101 and 110 degs., and between 121 and 130
degs., respectively. The aforementioned three values of the
correction amount Ea' are different with one another.
The correction amount Ea' is set to the different value depending
on the engine operation state in consideration with the increase in
the air resistance owing to sediments on the intake pipe 110 or the
exhaust pipe 120, which tends to vary with the engine operation
state. The sediments on the wall surface of the intake and exhaust
pipes 110, 120 may cause turbulence thereon. The turbulence may
further cause non-linear fluctuation in the air resistance value
depending on the intake air amount.
The control system of the second embodiment provides an
advantageous effect that compensates not only the reduced valve
lift amount owing to aging of the variable valve mechanism 320 but
also the change in the aerodynamic characteristics including the
increase in the air resistance (pressure loss) owing to aging of
the intake/exhaust mechanism 150 by correcting the operation angle
of the valve.
This embodiment may be applied not only to the subject that employs
the mechanism having the operation angle (valve opening interval)
.theta. adjusted by changing the valve lift amount but also to the
subject that employs the mechanism that allows the operation angle
.theta. to be changed independent from changing of the valve lift
amount. In this embodiment, the correction amount Ea' is calculated
in accordance with the engine operation state on the assumption in
contradiction to that of the first embodiment that the substantial
reduced valve lift amount is constant irrespective of the engine
operation state.
D. Valve Train Control System in the Third Embodiment
FIGS. 10A and 10B are explanatory views representative of a
correction amount Ea'' in a third embodiment of the invention. FIG.
10A shows each value of the correction amounts Ea'' calculated at
every valve-opening time area. FIG. 10B shows an example of the map
representing the relationship between the valve-opening time area
and the engine speed Ne.
The third embodiment is similar to the second embodiment in that a
plurality of values of the correction amount Ea'' are calculated as
shown in FIG. 10A. In the third embodiment, the valve-opening area
is used as the operating condition, which is different from that of
the second embodiment where the combination of the engine speed Ne
and the operation angle is used. The valve-opening time area is
expressed as the value obtained by integrating the valve lift
amount with time. It is calculated based on the engine speed Ne and
the operation angle in reference to the map.
FIGS. 11A and 11B are explanatory views representative of the
valve-opening time area used in the third embodiment of the
invention. FIG. 11A shows the relationship between the valve lift
amount of the intake valve 322 in the variable valve mechanism 320
and the crank angle .phi.. FIG. 11B shows the relationship between
the valve lift amount of the intake valve 322 and the time t. The
time t as the x-axis of the graph of FIG. 11B is obtained by
converting the crank angle .phi. as the x-axis of the graph of FIG.
11A using the engine speed Ne. The valve-opening time area
corresponds to the area defined by the x-axis and the curb
representing the valve lift amount in FIG. 11B.
In the mechanism where the operation angle .theta. is adjusted by
changing the valve lift amount, the dynamic characteristics of the
intake air become uniform irrespective of the engine speed Ne or
the operation angle .theta.. This is well known to those skilled in
the art experientially. In other words, even if the engine speed Ne
or the operation angle .theta. is changed, the dynamic
characteristics of the intake air are substantially uniform so long
as the valve-opening time area is kept uniform. This makes it
possible to perform the same correction. The aforementioned
mechanism employs the valve-opening time area as the operating
condition instead of the combination of the engine speed Ne and the
operation angle .theta..
The third embodiment employs a single parameter, that is, the
valve-opening time area instead of two parameters, that is, the
engine speed Ne and the operation angle so as to obtain the
correction value Ea'' at every operating condition. This makes it
possible to simplify the time-consuming calculation of the
correction value.
E. Fuel Supply Control System in Fourth Embodiment
FIG. 12 is a block diagram of a fuel supply control system in a
fourth embodiment of the invention. The fuel supply control system
of this embodiment for compensating the characteristic change of
the subject to be controlled owing to aging by correcting the fuel
supply quantity is different from the first to the third
embodiments for compensating the characteristic change by
correcting the operation angle of the valve. The correction of the
fuel supply quantity is performed on the basis of the concept of an
in-cylinder air charging ratio. The "in-cylinder air charging
ratio" represents the ratio of the amount of air admitted into the
combustion chamber in a single combustion cycle to the displacement
of the combustion chamber.
The fuel supply control system in the fourth embodiment employs an
air reduction ratio estimation section 15b in place of the valve
train mechanism estimation section 15 (see FIG. 3) or the
intake/exhaust state estimation section 15a (see FIG. 8). The air
reduction ratio estimation section 15b calculates the air reduction
ratio (A/B) so as to be transmitted to the fuel supply control
section 16.
The air reduction ratio (A/B) is obtained by dividing the first
charging efficiency A by the second charging efficiency B. The
first charging efficiency represents the in-cylinder air charging
ratio of the combustion chamber in the gasoline engine 100 after
the fluctuation owing to aging. The second charging efficiency
represents the in-cylinder air charging ratio of the combustion
chamber in the gasoline engine 100 before the fluctuation owing to
aging.
The air reduction ratio (A/B) is calculated by the air reduction
ratio estimation section 15b in the following manner. (1) The
substantial reduction in the valve lift amount is estimated. Based
on the estimated valve lift amount and the measurement value of the
air flow meter 130, the first charging efficiency A (charging
efficiency after aging) is calculated. The substantial reduction in
the valve lift amount is derived from the intake air pressure Ps,
the intake air flow rate Ms, the intake air temperature Ts input
from the intake/exhaust mechanism 150, the mechanical operation
amount .delta.a input from the actuator sensor 250, and the engine
speed Ne in the same manner as in the first to the fourth
embodiments. (2) The second charging efficiency B (charging
efficiency before aging) is calculated in accordance with the
measurement value of the air flow meter 130 on the assumption that
there is substantially no reduction in the valve lift amount. (3)
The air reduction ratio (A/B) is calculated by dividing the first
charging efficiency by the second charging efficiency.
The calculated air reduction ratio (A/B) is transmitted from the
air reduction ratio estimation section 15b to the fuel supply
control section 16 such that the fuel supply quantity is corrected
in accordance with the air reduction ratio (A/B). This makes it
possible to bring the air/fuel ratio into an optimum value.
It is clear that the invention may be applied to the structure that
compensates the characteristic change in the subject to be
controlled owing to aging not only by correcting the operation
angle of the valve but also by correcting the fuel supply
quantity.
This embodiment estimates the substantial value of reduction in the
valve lift amount as well as calculates the first charging
efficiency in accordance with the estimated reduction amount.
However, it may be structured to directly calculate the first
charging efficiency in response to the input from the
intake/exhaust mechanism 150 or the actuator sensor 250. The
aforementioned calculation may be performed by preparing the map
that directly represents the relationship between the input value
from the intake/exhaust mechanism 150 or the actuator sensor 250
and the first charging efficiency.
The internal combustion engine in the fourth embodiment is provided
with the variable valve mechanisms 320, 360. However, the invention
is applicable to the internal combustion engine that is not
provided with the variable valve mechanisms 320, 360. It is to be
noted that the invention provides a remarkable effect especially
when the internal combustion engine provided with the variable
valve mechanisms 320, 360 is employed because the characteristic
change in the aforementioned type of the internal combustion engine
owing to aging tends to become larger. The aforementioned internal
combustion engine is intended to be operated with relatively small
valve lift amount. In the aforementioned operation, the sediments
on the valve or the intake port of the combustion chamber is likely
to give a substantial influence on the in-cylinder charged air
amount.
F. Modified Example
The invention is not limited to the embodiments as aforementioned
but embodied in various forms without departing from spirit and
scope of the invention. For example, the invention may be modified
as described below.
F-1. In the valve adjustment mechanism of the respective
embodiments, the valve lift amount and the operation angle are
changed at the same timing. It may be structured to have one of the
valve lift amount and the operation angle adjustable. Generally the
valve adjustment mechanism employed in the invention may be
structured to have at least one of the valve lift amount and the
operation angle adjustable.
F-2. The respective embodiments are structured to compensate the
characteristic change owing to aging after production of the
intake/exhaust mechanism of the internal combustion engine. It is
possible to be structured to compensate the characteristic change
owing to variation in the individual products immediately after the
production or overhauling. It is possible to be structured to
estimate the characteristic change not only in the intake/exhaust
mechanism but also in the internal combustion engine as a whole.
The characteristic change in the internal combustion engine
corresponds to the difference of the state between the group of
internal combustion engines on the assumption that there is no
piece-to-piece variation based on an ideal concept and the actual
internal combustion engine to be controlled.
F-3. The invention is not limited to the engine provided with the
intake/exhaust variable valve timing mechanism but is applicable to
the engine having either the intake side or the exhaust side only
provided with the variable valve timing mechanism, or the engine
with no variable valve timing mechanism. The engine with the
variable valve timing mechanism may be operated at a relatively
smaller operation angle, and likely to be influenced by aging.
Therefore, the invention becomes effective especially for the
aforementioned type of the engine.
The invention is applied not only to the intake port injection
engine, but also to the in-cylinder injection engine. The air flow
meter (intake air flow rate detecting unit) is not limited to the
heat type air flow meter. The air flow meter of vane type or Karman
vortex type, for example may be employed.
* * * * *